The potential of DNA as a stable catalyst may give this molecule more success than ribozymes as tools for molecular biology, biotechnology, nanotechnology, and clinical diagnostics. Furthermore, comparison of catalytic RNA structures, which occurs naturally and more frequently, and DNA structures that result in catalytic motifs will prove crucial in revealing fundamental features of biocatalysts. To further gain insight into evolution and the structure and function of nucleic acid enzymes, this proposal will aim to 1) evolve a deoxyribozyme ligase from random sequences using stepwise evolution procedures, 2) optimize a deoxyribozyme-catalyzed ligase chain reaction (LCR), a method for the exponential amplification of target DNA through cycles of denaturing and annealing of ligation substrates and template, and 3) detect genetic mutations using the deoxyribozyme-catalyzed LCR, such as point mutations of BRCA1, BRCA1, and ones that give rise to beta-thalassemia. [unreadable] [unreadable] [unreadable]